Permanent hair colorants commonly come in two parts: a dye solution and a developer solution. In a conventional permanent hair coloring treatment, the dye solution and the developer solution are mixed and then immediately applied to the hair. After a time interval of about 25 to about 45 minutes, the hair is rinsed with water, treated with a post treatment conditioner, and then rinsed again with water.
The application of the dye solution and the developer solution affords permanent hair coloring. However, use of this conventional method does not provide maximum color deposition or retention and the range of color nuances especially in the red shades is limited.
The duration over which dyed hair remains colored is in principle only limited by the hair growth rate assuming the treatment does not affect the color of the hair as it is formed, i.e., the “roots”. In practice dye films deposited on the hair are susceptible to extraction by repeated shampooing, erosion by combing and brushing, and fading by exposure to sunlight and oxygen. Red colors are particularly susceptible to these degrading processes and in an attempt to achieve sufficiently deep and long lasting red shades consumers often try to compensate by increasing the intensity of the initial color. However, this can lead to hair that has an unnatural or painted appearance.
The underlying problem in achieving vibrant and natural colors especially dark reds, that are also long-lasting and fade resistant, through oxidative dyeing of hair is that only a small portion of such colors enters the interior of the hair fiber during the dyeing process. As is well known, the color of oxidative dyes arises from the oxidative coupling of primary intermediates and secondary intermediate (often called couplers)—essentially dimerization and/or polymerization. Thus, oxidative coupling leads to an increase in molecular weight as well as an increase in conjugation. However, as the molecular weight rises, it becomes increasingly difficult for the polymerized dye to penetrate the hair fibers. Thus, the darkest colors are more likely to remain at the surface of the hair fibers where they are most susceptible to erosion, and abrasion. Being on the outside of the fibers these colors are also in an “optical environment” that is least similar to the environment of the natural melanins in hair, i.e., dispersed within the hair fiber matrix. The term “painted” often used to describe the unnatural appearance of darkly dyed hair is more than coincidental!
It has been shown in U.S. Patent Publication U.S. 2003,0154,562 that a more long lasting and vibrant color is provided by a 2-step process in which oxidative dye precursors are applied to the hair in a substantially inactive form followed by the development of color with a composition that contains an oxidizing agent.
Although the 2-step process works well in terms of improved color retention and natural appearance it can require a relatively long contact time in the second developer step to achieve adequate lift or lightening when used on dark hair. The delivery of high lift is especially important to consumers with dark brown or black hair who desire to change the shade as well as the brightness of the hair. These consumers also have problems with conventional one-step process in terms of the fiber damage that is associated with strong bleaching systems.
A significant advantage of the present invention is that it provides a hair coloring method that not only will deliver long lasting, vibrant color but also deliver high lift or lightening especially on dark hair, coupled with a lower degree of fiber damage.
The following patents and publications have been considered:
U.S. Pat. No. 6,596,035 discloses a 1-step process for coloring the hair utilizing a combination of oxidative dyes a peroxide and a persulfate salt to simultaneously color and highlight the hair.
WO 93/03706 discloses a 1-step hair coloring composition including a coloring agent and a disaccharide that provides bleaching and coloring in a single step.
U.S. Pat. No. 6,440,177 discloses a 1-step process for coloring the hair utilizing water soluble basic azo dyes with a “category 2 bleach” which includes a persulfate salt. Oxidative dyes are stated to be unstable to such bleaching agents.
U.S. Pat. No. 5,980,586 discloses a 1-step process using a composition that includes an oxidative dye, a persulfate compound and an aminoethane thiol.
U.S. Patent Application Publication No. 2003/0188390 and U.S. Pat. No. 6,475,248 disclose specific direct dyes in combination with oxidizing agents in a 1-step hair coloring composition.
U.S. Patent Application Publication No. 2003/0166182 discloses a coloring system including a separately packaged thio compound, a mucuna plant extract, and an oxidizing agent.
U.S. Pat. No. 5,603,734 discloses a process for dyeing hair containing a cupric or ferrous salt, a catechol, and a persulfate oxidizing agent. The process is essentially carried out in one step.
None of the references cited above teaches that a sequential method for coloring the hair in which specific dyes in a predominantly non-anionic, and substantially oxidatively inactive form are first contacted with the hair followed by a developer lead to more vibrant colors and more varied tones.